An actor whose face you recognize from other movies but whose name you don't know. Once That Guy's anme becomes known, he ceases to be That Guy. That Guy alums include Joe Pantaliano, Steve Buscemi, CLint howard, etc.

"Hey! That Guy!" (said while watching Out For Justice and the Mexican goon with the tattoo on his neck walks onscreen)

The Urban Dictionary T-Shirt

a term given to a person who is in fact there, yet not there in person. the kind of person who when you see you're all like: Wow, he's in this class? and when they leave, you don't notice their absence.

The Urban Dictionary T-Shirt

That guy, is the person who enters an online video game just to mess with people. The "That Guy" is in every game room. He/She can range from someone who just messes around killing his teammates or someone with just a high pitch voice.

That Guy: Oops I killed my whole team again.
You: Oh great its That Guy.

Kid with high pitch voice: Hey guys are you ready for fun?!
You: We have officially found That Guy.

The Urban Dictionary T-Shirt

That guy, is the person who enters an online video game just to mess with people. The "That Guy" is in every game room. He/She can range from someone who just messes around killing his teammates or someone with just a high pitch voice.

That Guy: Oops I killed my whole team again.
You: Oh great its That Guy.

Kid with high pitch voice: Hey guys are you ready for fun?!
You: We have officially found That Guy.